The telecommunication industry is replacing old business models dictated by the public switched telephone network (PSTN) with Internet technologies, next generation networks, and new interconnect business models. Examples of this shift include the rapid deployment of voice over Internet protocol (VoIP) services, and the migration toward Internet protocol multimedia subsystems (IMS). In general, IMS services are implemented using a blended architecture of Internet technologies and wireless network capabilities to enable creation of new services within and across different wireless and wireline networks.
Currently, there are a number of telecommunication systems, methods, and services which integrate cellular and VoIP services. For example, U.S. Patent Application Nos. 2004/0240430, 2005/0096024, 2005/0129069, 2005/0117566, 2005/0186960, 2005/0147049, 2005/0152343, 2001/0015968 and U.S. Pat. Nos. 6,385,195 and 6,611,516 (each of which are hereby incorporated by reference in their entirety) disclose systems for switching between a cellular service and a VoIP service. Other known cellular-to-VoIP systems (e.g., U.S. Patent Application No. 2004/0240430, which is hereby incorporated by reference in its entirety) employ a PSTN-to-VoIP gateway which interfaces with the cellular telephone via a cellular wireless network and interfaces with the VoIP destination device via a VoIP network. The PSTN-to-VoIP gateway exchanges messages, call signaling, and audio media with the cellular telephone and the VoIP destination device to enable the cellular telephone to roam from the cellular wireless network to the VoIP network. U.S. Patent Application Nos. 2005/0096024 2005/0129069, 2005/0117566, 2005/0186960, 2005/0147049, 2005/0152343, 2001/0015968 and U.S. Pat. Nos. 6,385,195 and 6,611,516 (each of which are hereby incorporated by reference in their entirety) disclose additional telecommunication systems and methods which employ a PSTN-to-VoIP gateway for transitioning between a cellular service and VoIP service.
There are various existing commercial solutions for establishing a voice session from a cellular telephone to a VoIP destination device over the PSTN. One such solution uses a telephone number which is permanently assigned to a VoIP destination device. A cellular service subscriber enters the telephone phone number assigned to the VoIP destination device into their cellular telephone. The cellular telephone originates a voice call to the entered telephone number, which terminates at a PSTN-to-VoIP gateway. The gateway detects the called telephone number for the incoming call and sends an SIP INVITE message to the SIP URI permanently assigned to that telephone number. The VoIP destination device sends a SIP “ringing” reply to the gateway. The gateway sends a “ringing” indication to the cellular telephone. The VoIP destination device sends a SIP “success” reply to the gateway, if the session invitation is accepted (i.e., the “call” is answered). The gateway “answers” the incoming call from the cellular telephone and bridges the PSTN circuit to a VoIP media session with the VoIP destination device.
Another existing commercial solution, referred to as the iSkoot™ service, establishes a voice session between a cellular telephone and a VoIP destination device using the following process. The cellular telephone sends a text message or an e-mail (containing the cellular telephone number and the VoIP destination) to a PSTN-to-VoIP gateway. The PSTN-to-VoIP gateway originates a PSTN call to the cellular telephone number. The cellular telephone answers the incoming call from the PSTN-to-VoIP gateway. The PSTN-to-VoIP gateway sends a SIP INVITE message to VoIP destination. If the VoIP destination device is available and session invitation is accepted (i.e., the call is answered), a SIP “success” reply is sent to the PSTN-to-VoIP gateway. Then the PSTN-to-VoIP gateway bridges the PSTN call to the cellular telephone with the VoIP media session to the VoIP destination device.
Another commercial solution offered by Skype implements a peer-to-peer internet telephony software application. The software application enables peer-to-peer or computer-to-computer VoIP calls. The Skype™ service also offers a hosted, fee-based service, referred to as SkypeOut™, which allows computer users to initiate calls to non-computer-based landline or cellular telephones from a desktop application. Another hosted, fee-based service, SkypeIn™, allows computer users to receive incoming calls from non-computer-based landline or cellular telephones on their computer.
Another solution currently provided by EQO Communications (referred to as EQO Mobile Internet Phone Service for Skype™) enables mobile phone users to initiate VoIP calls from their mobile phone. The EQO software application on the mobile phone enables users to select Skype™ users from a buddy list. After the user selects the Skype destination, the software application sends an SMS to a personal computer configured with the Skype software. The PC initiates a Skype session to the VoIP destination. The PC calls the originating mobile phone number, and then the PC bridges the call to the VoIP destination.